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  1. #1
    Phil's Avatar
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    Question Sea Doo 215hp vs. Kawai 250hp

    Does anybody know the thrust an RXP generates? Kawai has published their thrust at over 1,540 ft. lbs. Also, I have read that the Kawai 250 has 250hp @ 7,750 rpm. Some people on the Ultra 250 thread have stated that the Kawai will turn 8,900 rpms! I think we had better get our facts straight here!

    For acceleration and top speed as well, THRUST and hull efficiency is the only thing that matters, not horsepower and not torque. You know Newton's theory, "Action and Reaction!" We are not turning wheels on pavement here and jet skis (PWCs) are not boats with propellers. There are specific formulas to calculate speed with boats and cars. I am not aware of any formula directly related to jetskis performance.

    I have heard theoretical speeds for the Ultra 250 as low as 62mph and as high as 82mph. My dealer told me that a stock 15F on our lake runs 61-62mph. If Kawai adds 5mph to that figure with the Ultra 250 based on a 60% thrust improvement, I wouldn't be a bit surprised. But a 10mph increase to 72mph may be a little too optimistic.


  2. #2

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    Unless kawi can figure out a new way to get the horsepower into the water it may touch 70.

  3. #3
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    72 stock will be a stretch. I'm guessing equal to an RXP in the 67-70 range with equal gas in each. I see it picking up quite a bit with an impeller because of the wide power band.

    Stock vs. Stock I think the Kawi is gonna beat a RXP pretty badly in a drag race. Kawi tends to focus more about acceleration that just top speed. My 15f only has about 170-175 hp and I out accelerate stock RXT's and run the same on the top end. They must match the pump really well to the motor.

  4. #4
    Flynfox's Avatar
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    Quote Originally Posted by AaronC View Post
    72 stock will be a stretch. I'm guessing equal to an RXP in the 67-70 range with equal gas in each. I see it picking up quite a bit with an impeller because of the wide power band.

    Stock vs. Stock I think the Kawi is gonna beat a RXP pretty badly in a drag race. Kawi tends to focus more about acceleration that just top speed. My 15f only has about 170-175 hp and I out accelerate stock RXT's and run the same on the top end. They must match the pump really well to the motor.
    My personal opinion based on the specs is that the Kawi will out accelerate the RXP, a stock one, but I doubt it will be significant, maybe a length. Remember the Kawi is heavier and the hull looks like it drags pretty deep, at least in the pics.

    On the street we have a saying "A chase is a race"...

  5. #5
    AaronC's Avatar
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    Quote Originally Posted by Flynfox View Post
    My personal opinion based on the specs is that the Kawi will out accelerate the RXP, a stock one, but I doubt it will be significant, maybe a length. Remember the Kawi is heavier and the hull looks like it drags pretty deep, at least in the pics.

    On the street we have a saying "A chase is a race"...
    Eh, I always race heads up. A fair race, is the only way to race in my book. Cause at the track the timeslips don't lie. If someone wants to get a running jump on me then I just let em go and don't try. When they slow down I'll roll up and ask if they want to do it right.

    The new kawi has a rideplate very similar to the R&D one I have which will help in chop, cornerning, acceleration, and top speed. I'm willing to bet it's gonna be more like 5-6 lengths. My 15f has about 1050 lbs of thrust currently and is 745 lbs. The new kawi is 1550ish on thrust and 903 lbs. Plus your talkin 11lbs of boost NOW and not 3-5-7 and hold, in a direct drive ski. I'm expecting top speed to be the same. Kinda like one guy running 12.20 at 115 and another running 11.8's at 115.

  6. #6
    Flynfox's Avatar
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    Quote Originally Posted by AaronC View Post
    Eh, I always race heads up. A fair race, is the only way to race in my book. Cause at the track the timeslips don't lie. If someone wants to get a running jump on me then I just let em go and don't try. When they slow down I'll roll up and ask if they want to do it right.

    The new kawi has a rideplate very similar to the R&D one I have which will help in chop, cornerning, acceleration, and top speed. I'm willing to bet it's gonna be more like 5-6 lengths. My 15f has about 1050 lbs of thrust currently and is 745 lbs. The new kawi is 1550ish on thrust and 903 lbs. Plus your talkin 11lbs of boost NOW and not 3-5-7 and hold, in a direct drive ski. I'm expecting top speed to be the same. Kinda like one guy running 12.20 at 115 and another running 11.8's at 115.
    Oh I agree with the fair race issue but these are not always real world conditions. 5-6 lengths! I seriously doubt it but I'm really anxious to find out so everybody can stop guessing.

    Here's a link I posted on another thread about the Pros & Cons of the diff superchanrger types: www.superchargersonline.com/content.asp?id=5.

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    AaronC's Avatar
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    I'm basing my opinion based on thrust vs. weight (just like RWHP/weight) and the instant and avg thrust. I'll use a gpr as an example and why you can't go by hp/weight only. It weighs 660 lbs has 170 hp and the most efficient hull at speed. My ski is 745 lbs and 170ish hp. The GPR has the power to weight ratio advantage, but I CRUSH stock GPR's by 10 lengths literally to top speed. The instant power my ski has, and the avg power it makes still over compensates the hp/weight disadvantage. And that's 2 ski's with roughly the same power. Kawi matches the power, powerband, to the pump very efficiently. It's like gearing a car to get to it's powerband quickly and stay there as long as it can.

  8. #8
    sleeplessnMS's Avatar
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    Stock vs stock I'll say the Kawi will win all the way around..... Just my .02 Now with a couple hundred dollars and sum of my tricks I dont know?

  9. #9
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    Well I agree somewhat. Keep in mind though the roots S/C is thermally ineficient so it may kill the hp. The general consensus, from what I've read, is that the Ultra will out accelerate the RXP but it won't blow it away.

    I actually considered the Ultra over my RXP but as soon as I saw the specs, weight, length etc, I was turned off as I prefer a smaller ski. My '06 GTI felt huge so I can't imagine how the Ultra would feel.

    Guess time will tell...

  10. #10
    Phil's Avatar
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    Quote Originally Posted by AaronC View Post
    I'm expecting top speed to be the same. Kinda like one guy running 12.20 at 115 and another running 11.8's at 115.
    If I read you right, you are saying that the 250 will be quicker than your ski or a stock RXP, but are you saying that the Ultra 250 will be about the same top speed as your ski? If so, how fast is your ski? What is your 0-60 or 0-50 time? It is an interesting comparision with your 1050lb. of thrust vs. the 250's 1540 lb. of thrust.... but do both skis have the same nozzle and are they pushing the same amount of water through the pump? Would you say that your 15F hull is more efficient than the 250's hull?
    Last edited by Phil; 10-17-2006 at 02:16 AM.

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